Hard disk drives are used in computers and other electronic devices for nonvolatile memory. A hard disk drive allows fast random access reading and writing of data to nonvolatile memory at a reasonable cost.
A hard disk drive usually consists of one or more platters coated with a magnetic material that can be polarized in order to store bits of information. A magnetic read/write head, which is attached to an actuator arm, reads and writes information to the disk surface. To access different tracks on the disk surface, the actuator arm pivots to change the radial location of the head relative to the center of the disk. A voice coil motor is commonly used to control the movement of the actuator arm.
Actuator arm assemblies commonly use pivot cartridge assemblies to allow the actuator arm to pivot relative to the hard drive disk. A pivot cartridge usually consists of a sleeve, usually made of stainless steel, two or more bearings, and a shaft.
FIG. 1 shows a prior art pivot cartridge 10 and actuator arm 12. The actuator arm 12 holds the voice coil 14, which is used for controlling movement. The actuator arm 12 may be attached to the pivot cartridge 10 with an adhesive applied to an inner surface 13 of the actuator arm 12, with a mechanical fastener such as a screw 20 threaded into the actuator arm 12 at a threaded hole 22, or with a compression ring (c-ring) 16 and spring washer 18 combination.
FIG. 2 shows a cross section of a typical prior art pivot cartridge 10. In this example the actuator arm 12 and pivot cartridge 10 are assembled with a c-ring 16 and spring washer 18. The pivot cartridge 10 includes a sleeve 30, an upper bearing 26, a lower bearing 24, and a shaft 28. The shaft 28 has a flange 29 that separates the upper bearing 26 and lower bearing 24. The bearings 24, 26 are usually attached to the sleeve 30 with an adhesive. Typically, a preload force (500 g for example) is applied to the pivot cartridge assembly 10 while the adhesive cures. Adhesives are used, because the relatively high preload force cannot be maintained with other methods such as a frictional or interference fit. A suitable adhesive is an ultraviolet light curing adhesive such as Loctite 648UV.
The sleeve of a typical pivot cartridge, which may have a wall thickness of less than 1 mm, is very expensive to manufacture. If the sleeve could be eliminated from the actuator arm pivot assembly, the disk drive manufacturing cost would be significantly reduced. Thus, there is a need for a sleeveless actuator arm pivot assembly.